Thermal evolution and geometry of the descending lithosphere beneath the SE-Carpathians: An insight from the past
Thermal evolution and geometry of the descending lithosphere beneath the SE-Carpathians: An insight from the past
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DOI：
10.1016/j.epsl.2008.06.012
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发表时间：
2008-08-30
影响因子：
5.3
通讯作者：
Korotkii, Alexander
中科院分区：
文献类型：
--
作者：
Ismail-Zadeh, Alik;Schubert, Gerald;Korotkii, Alexander
由地震层析成像得到的喀尔巴山东南部地区的地幔不均质性包含有关地幔现今热状态的信息。基于P波地震速度异常，建立了该地区现今地幔温度模型，并将该模型与受热流数据约束的地壳温度模型相结合。利用早中新世和中新世区域运动的信息，将模拟的温度同化到地质过去。在该地区下降的岩石圈板块的突出热状态从其弥散的现在状态恢复过来。在中新世时期，板块几何结构清楚地显示了下沉体的两部分。地体的西北-东南向部分位于东欧地台与西西期地台边界附近，这部分下沉地体可能是向东移动的冷岩石圈的遗迹。另一部分为北东-西南向，与现今的下降板有关。在60公里的深度以上，板材具有凹形的热形状，证实了喀尔巴斯山弧形的曲率，而在该深度以下有一个凸面。在大约220公里的深度将其一分为二之前，该板块一直保持着其凸起的形状。我们认为，这种可能一直保存到现在的板块几何形状的变化，可能会由于板块弯曲和随后的应力释放而导致应力局部化，从而导致该地区发生大的地幔地震。我们还假设，岩石圈下沉板块的脱水和部分熔融过程或板块从邻近最上地幔拖曳较热岩石的过程可能是特兰西瓦尼亚盆地下方地震速度降低的原因。(C)2008爱思唯尔B.V.保留所有权利。
Mantle heterogeneities imaged by seismic tomography in the SE-Carpathians contain information on the present thermal state of the mantle. Based on P-wave seismic velocity anomalies we develop a model of the present mantle temperature beneath the region and combine the model with a model of crustal temperature constrained by heat flow data. The modeled temperatures are assimilated into the geological past using the information on the regional movement in the Early and Middle Miocene. Prominent thermal states of the lithospheric slab descending in the region are restored from its diffuse present state. In Miocene times the slab geometry clearly shows two portions of the sinking body. The northwest-southeast oriented portion of the body is located in the vicinity of the boundary between the East European and Scythian platforms, and this portion of the sinking body may be a relic of cold lithosphere that has traveled eastward. Another portion has a northeast-southwest orientation and is related to the present descending slab. Above a depth of 60 km the slab had a concave thermal shape, confirming the curvature of the Carpathian arc, and a convex surface below that depth. The slab maintained its convex shape until it split into two parts at a depth of about 220 km. We propose that this change in the slab geometry, which is likely to be preserved until the present, can cause stress localization due to the slab bending and subsequent stress release resulting in large mantle earthquakes in the region. Also we hypothesize that either the processes of dehydration and partial melting of the descending lithospheric slab or dragging down of hotter rocks from the adjacent uppermost mantle by the slab are possible causes of the reduction in seismic velocities beneath the Transylvanian Basin. (C) 2008 Elsevier B.V. All rights reserved.